RE: Recoil project
Put the rifle in a rest and put the butt against an object of a specific weight. Put the weight on something that will roll or slide. Fire the rifle and measure the amount it moved the object backwards. This may not tell you exactly how much recoil the weapon has, but it will give you a comparison between the different loads as long as the same weight object is used in each test.
This isn't real scientific since there are quite a few variables and things to take acount for like friction and stuff like that. However it should make a decent presentation for a highschool project.
You could also do the math shown above and estimate how far the object should move in theory and compare it to what it does in real life. You may have to take into acount for the weight of the rifle as well. Maybe even the rest depending on how much it restricts the movement of the rifle.
Paul